You can attach SSRS instance to CRM through using SSRS Connector. With regard to RDL files you will have to reinstall it on new SSRS server.
To install the Microsoft Dynamics CRM 4.0 Connector for SQL Server Reporting Services, locate the Microsoft Dynamics CRM installation files, and follow these steps:
In the /SrsDataConnector/ folder, double-click SetupSrsDataConnector.exe.
On the Welcome to Microsoft Dynamics CRM Connector for SQL Server Reporting Services Setup page, select whether you want to update Microsoft Dynamics CRM Server Setup. We recommend that, if updates are available, you let Setup download the latest version. To do this, click Update installation files, wait until the update process is complete, and then click Next.
On the License Agreement page, review the information and, if you accept the license agreement, click I accept this license agreement, and then click I Accept.
If Setup detects that components are missing, the Install Required Components page appears.
If you have already installed the required components, this page will not appear.
If you have not installed the required components listed, you can install them now. Click Install. When the components are installed, the status column will change from Missing to Installed, and you can click Next to continue.